.\" Copyright (C) 2000, 2001, 2003-2005, 2007, 2014-2016, 2018-2020 Internet Systems Consortium, Inc. ("ISC")
.\" 
.\" This Source Code Form is subject to the terms of the Mozilla Public
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.\"     Title: lwres_context
.\"    Author: 
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\"      Date: 2007-06-18
.\"    Manual: BIND9
.\"    Source: ISC
.\"  Language: English
.\"
.TH "LWRES_CONTEXT" "3" "2007\-06\-18" "ISC" "BIND9"
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.SH "NAME"
lwres_context_create, lwres_context_destroy, lwres_context_nextserial, lwres_context_initserial, lwres_context_freemem, lwres_context_allocmem, lwres_context_sendrecv \- lightweight resolver context management
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <lwres/lwres\&.h>
.fi
.ft
.HP \w'lwres_result_t\ lwres_context_create('u
.BI "lwres_result_t lwres_context_create(lwres_context_t\ **" "contextp" ", void\ *" "arg" ", lwres_malloc_t\ " "malloc_function" ", lwres_free_t\ " "free_function" ");"
.HP \w'lwres_result_t\ lwres_context_destroy('u
.BI "lwres_result_t lwres_context_destroy(lwres_context_t\ **" "contextp" ");"
.HP \w'void\ lwres_context_initserial('u
.BI "void lwres_context_initserial(lwres_context_t\ *" "ctx" ", uint32_t\ " "serial" ");"
.HP \w'uint32_t\ lwres_context_nextserial('u
.BI "uint32_t lwres_context_nextserial(lwres_context_t\ *" "ctx" ");"
.HP \w'void\ lwres_context_freemem('u
.BI "void lwres_context_freemem(lwres_context_t\ *" "ctx" ", void\ *" "mem" ", size_t\ " "len" ");"
.HP \w'void\ lwres_context_allocmem('u
.BI "void lwres_context_allocmem(lwres_context_t\ *" "ctx" ", size_t\ " "len" ");"
.HP \w'void\ *\ lwres_context_sendrecv('u
.BI "void * lwres_context_sendrecv(lwres_context_t\ *" "ctx" ", void\ *" "sendbase" ", int\ " "sendlen" ", void\ *" "recvbase" ", int\ " "recvlen" ", int\ *" "recvd_len" ");"
.SH "DESCRIPTION"
.PP
\fBlwres_context_create()\fR
creates a
\fBlwres_context_t\fR
structure for use in lightweight resolver operations\&. It holds a socket and other data needed for communicating with a resolver daemon\&. The new
\fBlwres_context_t\fR
is returned through
\fIcontextp\fR, a pointer to a
\fBlwres_context_t\fR
pointer\&. This
\fBlwres_context_t\fR
pointer must initially be NULL, and is modified to point to the newly created
\fBlwres_context_t\fR\&.
.PP
When the lightweight resolver needs to perform dynamic memory allocation, it will call
\fImalloc_function\fR
to allocate memory and
\fIfree_function\fR
to free it\&. If
\fImalloc_function\fR
and
\fIfree_function\fR
are NULL, memory is allocated using
\fBmalloc\fR(3)\&. and
\fBfree\fR(3)\&. It is not permitted to have a NULL
\fImalloc_function\fR
and a non\-NULL
\fIfree_function\fR
or vice versa\&.
\fIarg\fR
is passed as the first parameter to the memory allocation functions\&. If
\fImalloc_function\fR
and
\fIfree_function\fR
are NULL,
\fIarg\fR
is unused and should be passed as NULL\&.
.PP
Once memory for the structure has been allocated, it is initialized using
\fBlwres_conf_init\fR(3)
and returned via
\fI*contextp\fR\&.
.PP
\fBlwres_context_destroy()\fR
destroys a
\fBlwres_context_t\fR, closing its socket\&.
\fIcontextp\fR
is a pointer to a pointer to the context that is to be destroyed\&. The pointer will be set to NULL when the context has been destroyed\&.
.PP
The context holds a serial number that is used to identify resolver request packets and associate responses with the corresponding requests\&. This serial number is controlled using
\fBlwres_context_initserial()\fR
and
\fBlwres_context_nextserial()\fR\&.
\fBlwres_context_initserial()\fR
sets the serial number for context
\fI*ctx\fR
to
\fIserial\fR\&.
\fBlwres_context_nextserial()\fR
increments the serial number and returns the previous value\&.
.PP
Memory for a lightweight resolver context is allocated and freed using
\fBlwres_context_allocmem()\fR
and
\fBlwres_context_freemem()\fR\&. These use whatever allocations were defined when the context was created with
\fBlwres_context_create()\fR\&.
\fBlwres_context_allocmem()\fR
allocates
\fIlen\fR
bytes of memory and if successful returns a pointer to the allocated storage\&.
\fBlwres_context_freemem()\fR
frees
\fIlen\fR
bytes of space starting at location
\fImem\fR\&.
.PP
\fBlwres_context_sendrecv()\fR
performs I/O for the context
\fIctx\fR\&. Data are read and written from the context\*(Aqs socket\&. It writes data from
\fIsendbase\fR
\(em typically a lightweight resolver query packet \(em and waits for a reply which is copied to the receive buffer at
\fIrecvbase\fR\&. The number of bytes that were written to this receive buffer is returned in
\fI*recvd_len\fR\&.
.SH "RETURN VALUES"
.PP
\fBlwres_context_create()\fR
returns
\fBLWRES_R_NOMEMORY\fR
if memory for the
\fBstruct lwres_context\fR
could not be allocated,
\fBLWRES_R_SUCCESS\fR
otherwise\&.
.PP
Successful calls to the memory allocator
\fBlwres_context_allocmem()\fR
return a pointer to the start of the allocated space\&. It returns NULL if memory could not be allocated\&.
.PP
\fBLWRES_R_SUCCESS\fR
is returned when
\fBlwres_context_sendrecv()\fR
completes successfully\&.
\fBLWRES_R_IOERROR\fR
is returned if an I/O error occurs and
\fBLWRES_R_TIMEOUT\fR
is returned if
\fBlwres_context_sendrecv()\fR
times out waiting for a response\&.
.SH "SEE ALSO"
.PP
\fBlwres_conf_init\fR(3),
\fBmalloc\fR(3),
\fBfree\fR(3)\&.
.SH "AUTHOR"
.PP
\fBInternet Systems Consortium, Inc\&.\fR
.SH "COPYRIGHT"
.br
Copyright \(co 2000, 2001, 2003-2005, 2007, 2014-2016, 2018-2020 Internet Systems Consortium, Inc. ("ISC")
.br
